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Greatest common factor worksheets

The greatest common factor is the largest number that divides two values evenly — the key to simplifying fractions and factoring later on. These free printable worksheets ask a child to find the GCF of a set of numbers, listed compactly one set per line.

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Ready for harder? GCF & LCM puzzles — the GCF and the LCM are given and the two numbers are not.

Greatest common factor
Greatest common factor worksheet — 2 or 3 numbers, free printable with answer key

The answer key prints on a separate page.

What's on this sheet

Every set is built to share a real factor greater than one, and no number divides another, so the answer is never trivially the smallest number and never just one. That construction keeps the practice honest: a child has to actually compare factors rather than read the answer off the page. Choose two numbers or three, and set the size with the level control.

Why this sheet works

The sheet follows the clean worksheet convention — the instruction is stated once at the top, and each line simply lists the numbers with an arrow to the answer (42, 54 → GCF = __) instead of repeating the full sentence every row. That keeps a page of practice quick to scan. The answer key prints the GCF for every set.

How this one works

One question from this sheet, worked through a step at a time.

GCF of 12 and 30

12:1234612
12:1234612
30:12356101530
12:1234612
30:12356101530
12:1234612
30:12356101530
GCF=6
  1. A factor is a number that divides in exactly. List every factor of 12.
  2. Now every factor of 30.
  3. Some appear in BOTH lists — 1, 2, 3, 6. Those are the common factors.
  4. The greatest of them is 6, so the GCF of 12 and 30 is 6.

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